1. Field of the Invention
The present invention relates to a supply construction in a combinatorial weighing apparatus having a number of weighing machines disposed in a circular pattern and supplied with articles such as pieces of cheese or jelly charged downwardly for weighing these articles according to preset weights.
2. Description of the Prior Art
In the field of material handling, it is widely practiced to handle various articles of merchandise as units having preset or unfixed weights. For example, a technique has widely been employed for weighing and packaging many particles such as snack foods or candies as units according to preset weights.
The applicant has alreadly invented various combinatorial weighing apparatus and filed patent applications in various countries for such combinatorial weighing apparatus. In weighing particles, it is not permissible from the standpoint of business to package them as a unit which has an actual weight smaller than a preset weight. Therefore, it is important for the combinatorial weighing apparatus to weigh particles so as to give a weight which is slightly larger than the preset weight.
According to U.S. Pat. No. 4,399,880, a combinatorial weighing apparatus has ten weighing hoppers, for example, arranged in a circular pattern and supplied randomly with articles to be weighed. The weights are combined and weight combinations are selected to find an optimum weight combination which is slightly greater than a preset weight according to the theory and experiences of probability and statistics. FIG. 1 of the accompanying drawings shows such a disclosed combinatorial weighing apparatus. The combinatorial weighing apparatus, generally designated at 1, has a frame 2 on which an upper frame 4 is mounted by a subframe 3. The upper frame 4 supports on its central portion a conical disk-shaped distributing table 6 disposed below an article charger 5 positioned above the frame 2, the distributing table 6 being mounted on a vibrator 7 which is reciprocally vibratable through a prescribed angle in a circumferential direction. A plurality of (such as ten) troughs 8 (only two shown in FIG. 1) are disposed radially around the distributing table 6 and supported by suitable electromagnetic vibrators 9. The troughs 8 have their radially outward discharge ends positioned in pool hoppers 10, respectively, which have outlets opening toward weighing hoppers 12 supported on weight detectors 11 mounted on the frame 2 and including known load cells or the like. The weighing hoppers 12 have outlets opening toward lower collection chutes 13, 14.
Articles to be weighed which are carried on a conveyor or the like are charged from the charger 5 onto the distributing table 6. The distributing table 6 is reciprocally vibrated and turned through the given angle in the circumferential direction to distribute the articles as uniformly as possible into the troughs 8 through which the articles are supplied into the pool hoppers 10. The pool hoppers 10 are controlled by driver units 15 supported on the upper frame 4 for opening and closing their lids to feed the articles into the weighing hoppers 12, whereupon the supplied articles are weighed by the weight detectors 11. Those weighing hoppers 12 which give an optimum weight combination that is slightly larger than a preset weight are determined by a microcomputer (not shown). These selected weighing hoppers 12 are driven by the driver units 15 controlled by a control unit to open their lids for discharging the articles into either the collection chute 13 or 14 from which the articles are delivered to a packaging machine, not shown.
In the above process, no correct weighing and combinatorial operation would be carried out unless the articles were supplied from the distributing table 6 substantially uniformly into the troughs 8.
As shown in FIG. 1, the internal construction of the combinatorial weighing apparatus 1 is complex especially because of the necessity for enabling the apparatus to take up a reduced space. Therefore, if articles were to overflow from the vibrating distributing table 6 into the apparatus construction, the apparatus 1 would be caused to malfunction, and would have to be maintained and inspected at frequent intervals.
The distributing table 6 has a conical shape generally formed by pressing and hence has a simple slanted surface. The distributing table 6, when vibrated and turned, supplies the articles from its slanted conical surface substantially uniformly into the troughs 8 arranged around the distributing table 6. As shown in FIG. 1, the troughs 8 are mounted on the electromagnetic vibrators 9 so that only those troughs 8 which have been selected to give an optimum weight combination and have discharged the articles in a preceeding weighing cycle will be vibrated radially so as to be supplied with articles again. The bottoms of the troughs 8 are disposed downwardly of the peripheral edge of the distributing table 6. Articles to be distributed into the troughs 8 are temporarily stored on the distributing table 6 before they are supplied into the troughs 8. When certain weighing hoppers 12 are selected, the corresponding troughs 8 are radially vibrated to advance the articles. If some of the weighing hoppers 12 are selected less frequently, then articles in the corresponding troughs 8 tend to be deposited therein and overflow from the rear ends of the troughs 8 onto the upper frame 4. If some weighing hoppers 12 are selected too frequently, then the corresponding troughs 8 are liable to run short of articles.
Where articles such as pieces of cheese or jelly having sticky surfaces are to be weighed, the distributing table having the slanted suface designed to store the articles temporarily thereon tends to distribute and supply the sticky articles irregularly as masses. Since the central portion of the distributing table as it is vibrated spirally is moved more vertically than circumferentially, articles are apt to remain deposited on the central portion of the table rather than being distributed radially outwardly. When such deposited articles are in excess of a certain limit, they collapse together and are supplied irregularly into the troughs.
Therefore, in order to cope with the prior combinatorial weighing apparatus drawbacks discussed above, the apparatus has been required to be seviced and inspected frequently during normal operation.